Blood primarily consists of red blood cells in suspension in plasma, a Newtonian fluid.
The distribution of red blood cells within a given vessel, or from one vessel to another, is far from homogeneous, and the way they split at the vessels junctions is a very complex issue.
This lab-course enables the participant to observe and understand the mechanisms driving the behaviour of red blood cells, in particular their distribution in the complex network of capillaries, through microfluidic experimentations and dedicated set ups.
This lab-course is suited to students from the L3 level with a background in fluid mechanics.
Measure blood viscosity in a confined microfluidic channel serving as a micro viscosimeter
4 hrs session
In this module, a simple Y shaped PDMS microfluidic set-up is used to create a co-flow with a reference fluid of known viscosity and blood.
The flow is observed by light transmission microscopy and blood cells concentrations are calculated as a function of the transmitted light intensity using the Beer-Lambert law.
By varying experimental parameters such as the channels width or the fluid flow rates, and using the reference fluid viscosity as a standard, the participants can infer blood viscosity and assess its dependence on the blood cells concentration, the shear rate and the confinement.
Haematocrit: study the evolution of blood cells concentrations in a model circulatory network
4 hrs session
In this part, a higher level of complexity is reached thanks to an experimental set-up reproducing the complex network of vessels in which blood circulates.
The observations show that the haematocrit (blood cells concentration) is very heterogeneous in the network from one branch to another.
The origin of the asymmetric splitting of the cells at a channels' bifurcation is experimentally tested and the agreement of the experimental data with the existing models which attempt to predict the final haematocrit in each branch of a given circuit as a function of the inlet haematocrit, the viscosity of the fluid and the flow rate is discussed.